Violacein transformation by peroxidases and oxidases: implications on its biological properties

1,3-Dihydro-2 H-indol-2-one derivative (violacein) is extracted from Chromo bacterium violaceum and presents several biological activities as antibioti c, antitumoral, antichagasic and antioxidant. In order to increase its biol ogical activities and decrease its toxicity, one strategy is to slightly tr ansform the molecules through a specific group transformation. Peroxidases, which are hemoproteins, are known as excellent oxidants producing hydroxyl ation and ring cleavage. Laccases are phenol oxidases produced by fungi as plants and belong to the oxidase group which complexes copper. This enzyme generates phenolates, quinones and also ring cleavage even in the presence of a mediator as 1-hydroxybenzotriazol (HBT). Lignin peroxidase and mangane se peroxidase (LiP/MnP) pool from Phanerochaete chrysosporium, Horseradish peroxidase (HRP-VI) from horseradish, Lactoperoxidase (LPO) from bovine mil k and Laccase (Lac) from Trametes versicolor acting on violacein were studi ed. Kinetics parameters and products distribution indicated a fast and effi cient violacein transformation with all of them. HRP-VI acting on violacein was studied in details and spectral evidence indicated that Horseradish pe roxidase compound II was formed during the oxidation reaction. Similar beha vior with LiP/MnP pool was observed. Laccase, in the presence and absence o f mediator (HBT), also showed a rapid violacein transformation. In a more d etailed study with the HRP-VI reaction, a hydroxilation in the indol unit a nd a ring contraction of the pyrrol moiety of violacein molecule occurred. (C) 2001 Elsevier Science B.V. All rights reserved.